EDENVILLE, Mich. – Crews have started emergency construction work on a portion of a central Michigan dam that collapsed last spring and contributed to flooding that destroyed homes and forced the evacuations of about 10,000 people. Excavation work will be done below the Edenville Dam in Midland County, according to state officials. The dam failed during a steady rain in May, draining Wixom Lake and unleashing the Tittabawassee River, which then overwhelmed the Sanford dam, about 140 miles (225 kilometers) north of Detroit. Work also is being done inside the Tobacco River spillway in Gladwin and Midland counties to prepare it for being lowered by 21 feet (6.4 meters), officials said. The Edenville Dam is classified as a high hazard dam.